There have widely been used corrugators having a constitution wherein a corrugating medium is allowed to have a corrugation with a desired pitch size; said medium is then pasted together with a liner at the crests of corrugation using an adhesive to form a single-faced corrugated board sheet; and the thus obtained single-faced corrugated board sheet is further pasted with a back liner to form a double-faced corrugated board sheet. In such type of corrugators, a single facer for forming a single-faced corrugated board sheet and a double facer for pasting the thus formed single-faced corrugated board sheet with a back liner are used as main devices. Further, indispensable as incidental equipments are cardboard web feeding devices for feeding cardboard webs such as corrugating medium, liner and back liner (these cardboard webs are hereinafter referred to as "web").
These webs are loaded to web feeding devices, in the form of rolls each having predetermined diameters taken up around core paper tubes (hereinafter referred to as "web rolls"), from which the webs are delivered or fed out. Further, in accordance with the order change in the corrugated board sheet to be formed during the process of production, the web rolls are removed from the web feeding devices and loaded on conveying means such as a flat car etc. to be carried out to a specified stockroom.
As a prior art web feeding device to be employed in a corrugator, a mill roll stand of so-called swing arm system as shown in FIG. 21 is widely known. The mill roll stand shown with the numeral 10 comprises two pairs of swing arms 13, each pair comprising right and left arms being connected to horizontal pivotal shafts 11 and 12, respectively, by means of splines. The respective arms 13 have a center block 16 at the tip such that it may oppose its counterpart provided on the other arm 13, and can be fitted into the end portions of a paper tube 15 of a web roll 14.
Carry-in/out tracks 17 are defined on the ground of the factory site, extending from the mill roll stand 10 toward two opposing directions, for carrying the web rolls 14 to and from said mill roll stand. These carry-in/out tracks 17 each comprises a pit formed by digging the ground of the factory site down to a predetermined depth to extend parallel to the pivotal shafts 11 and 12, to which pit a flat car 18 is disposed such that it can travel freely along said pit. The flat car 18 has a table 19 on the top for loading the web roll 14 thereon, and only the table 19 appears above said pit.
To achieve loading of a web roll 14 onto one pair of swing arms 13 supported by the right side pivotal shaft 12 in said mill roll stand 10, the flat car 18 carrying the web roll 14 thereon is allowed to travel along the right side carry-in/out track 17 until it reaches below the swinging loci of said swing arms 13; wherein the swing arms 13 are spaced from each other, and in this state the right side pivotal shaft 12 is turned clockwise until the center blocks 16 may be aligned with the center of the paper tube 15 of the web roll 14.
Subsequently, the swing arms 13 are moved closer to each other to effect chucking of the paper tube 15 of the web roll 14 by means of the center blocks 16, and then the arms 13 are swung counterclockwise upwardly, whereby loading of the web roll 14 (also referred to as "web setting") is achieved. Likewise, the same procedures can be applied to the other pair of swing arms 13 supported on the left side pivotal shaft 11 to load another web roll 14 thereto. The web delivered from the web roll 14 loaded onto the one pair of the swing arms 13 is fed to a predetermined portion of a corrugator not shown.
When the web roll 14 loaded onto the swing arms 13 is unloaded from said arm for returning to the stockroom, or the web roll 14 under loading is replaced with another web roll 14 of a different standard in accordance with the order change during the operation of the line, the swing arms 13 locating at its upper position is swung downward until they may reach immediately above the flat car 18 which is waiting on the carry-in/out track 17. Next, the arms 13 are opened to release chucking against the web roll 14 to load said web roll 14 onto the table 19 of the flat car 18. The swing arms 13 are then swung upward to assume again the upper position and moved farther from each other to wait for the next web roll 14 to be chucked therebetween. Subsequently, the flat car 18 carrying the web roll 14 loaded thereon retracts the carry-in/out track 17 toward the specified stockroom.
When a new web roll 14 is successively loaded, the flat car 18 carrying the web roll 14 thereon travels along the carry-in/out track 17 until it reaches below the swinging loci of the swing arms 13, and loading of the web roll 14 against the arms 13 is achieved in the order as described above.
Thus, in a web feeding device of a conventional mill roll stand system wherein a conveyer for transporting web rolls is disposed at an outer area relative to each of the two pairs of swing arms, respectively, the swing arms 13 are swung diagonally downward after a new web roll 14 is carried in, to effect centering of the center blocks 16 with the paper tube 15 of the web roll 14, and then both arms are moved closer to each other to effect chucking of the web roll 14 therebetween, as described above. Next, the two arms 13 are swung diagonally upward to complete loading of the web roll 14.
On the other hand, when a web roll 14A supported by the two swing arms 13 under delivery is replaced with a different new web roll 14B, chucking against the web roll 14A is released after the two swing arms 13 are swung diagonally downward. While the former web roll 14A is carried out after the arms 13 are swung diagonally upward, these arms 13 must be waiting in the above posture, i.e. in an upwardly tilted posture, for the time until carrying in of the new web roll 14B is completed. After the new web roll 14B is carried in, the swing arms 13 are swung diagonally downward to effect centering of the center blocks 16 with the paper tube 15 of the web roll 14B. Subsequently, the two arms 13 are moved closer to each other to chuck the web roll 14B therebetween, and then they are swung upward again to achieve loading of the new web roll 14B.
Thus, for the replacement of web rolls, it is necessary not only to reciprocate the swing arms horizontally along the pivotal shaft but also to allow them to be waiting at the said position in an upwardly tilted posture for the time until completion of carrying out of the former web roll and carrying in of the new web roll. Accordingly, under the present circumstances, the web setting operation requires quite a lot of time loss. Therefore, in the corrugated board sheet production industries in which there is a necessity for coping with frequent order change due to small lot productions, reduction of the time cycle to be required for the replacement of web rolls is extremely important. In this respect, no prior art web feeding device could sufficiently meet such demand.